ROTTERDAM, the Netherlands — In what came as no surprise to the other riders at the Tour de France, the Swiss cyclist Fabian Cancellara won the Tour’s prologue on Saturday, earning the yellow leader’s jersey to kick off the three-week race.

Cancellara is a time-trial specialist, known for thick, powerful thighs knotted with muscles. As the Olympic time trial champion and the world time trial champion, Cancellara is considered the rider to beat in the Tour’s prologue.

Yet the International Cycling Union on Saturday wanted to make sure that Cancellara’s speedy, 10-minute victory on the 5.5-mile course was not too good to be true. Suspicions of motorized cheating arose this season, fueled by Cancellara’s dominant victories at Paris-Roubaix and the Tour of Flanders.

So, soon after Cancellara crossed the finish line Saturday, officials grabbed his bike, took it to a nearby tent and X-rayed it, checking to see if there was a tiny motor inside. His was one of 14 bikes X-rayed Saturday. All passed the inspection.

Cancellara, of the Saxo Bank team, called the need for the X-ray “ridiculous,” saying the accusations against him were false. Before the race, Pat McQuaid, the cycling union’s president, explained the need for the inspection.

“I honestly don’t believe that there has ever been a motorized bike in the peloton because the technology is not there yet to do it secretly,” McQuaid said, adding that a motor’s battery would not fit inside a bike’s frame. “But in cycling, if the suspicions are there, we’ve learned that we have to deal with those suspicions. These, like the others, are just another cloud over the sport that has dampened the sport. We’re doing all we can to get rid of those clouds.”

Fittingly, the prologue began in rain, under a gray sky. Tony Martin, a German rider for HTC-Columbia, rode early, setting the standard of 10 minutes 10 seconds. He ended up second. David Millar, a British rider for Garmin-Transitions, finished third, at 10:20.

Lance Armstrong, who at 38 says he is racing in his final Tour de France, took to the course near the end of the day. He finished fourth, 22 seconds behind Cancellara — but 5 seconds ahead of his rival Alberto Contador, who was sixth.

Afterward, Armstrong said, “In my heart it was a surprise” that he had fared so well. Despite the plucky ride, a dark cloud loomed over him, too — not one prompted by motorized doping, but by questions about conventional doping.

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The Dutch cyclist Maarten Tjallingii was one of 197 riders in the Tour de France’s five-and-a-half-mile prologue stage in Rotterdam.Credit
Eric Gaillard/Reuters

Early Saturday, The Wall Street Journal reported more details of an accusation that Armstrong participated in systematic doping in the early 2000s. In the article, Floyd Landis, who was stripped of his 2006 Tour title for testosterone use, gave an account of his and other riders’ doping regimens while on the United States Postal Service team.

Landis’s initial accusation of doping became news in May when a series of leaked e-mail messages from him to top cycling officials became public. Now a federal investigation is looking into whether Armstrong and his associates committed fraud and used team money to finance doping. Armstrong has vehemently denied Landis’s allegations.

In Saturday’s article, Landis told The Journal that Armstrong’s team once sold 60 of the bikes given to them by their sponsor, Trek, to finance the team’s systematic doping.

Yet Armstrong seemed unfazed. At 9:22 a.m. Rotterdam time, his manager, Mark Higgins, sent a statement from Armstrong via e-mail, saying that the continued doping accusations were “the same old news from Floyd Landis, a person with zero credibility.”

The statement also said, “Landis’s credibility is like a carton of sour milk: once you take the first sip, you don’t have to drink the rest to know it has all gone bad.”

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Dutch cycling fans arrived early Saturday to see the prologue of the Tour de France. The first stage is Sunday, from Rotterdam, the Netherlands, to Brussels.Credit
Robin Van Lonkhuijsen/ANP, via European Pressphoto Agency

Hours later, Armstrong arrived at the staging area. His girlfriend, Anna Hansen, and his young son, Max, also showed up, hanging around the bus of Armstrong’s team, RadioShack. The president of Trek Bicycle, John Burke, was also there, happily chatting with members of Armstrong’s entourage.

After his ride, Armstrong said Landis’s claims had neither angered nor inspired him.

“It’s been 10 years, 10 years,” he said, referring to the doping allegations that have followed him through much of his career. “It’s nothing new.”

Bob Stapleton, the owner of the HTC-Columbia team, said he was not surprised that so much controversy has again disrupted the sport. He smiled and said that the Tour de France just would not be the same without it.

That may be true. This is not the first time the Tour, in its 97th edition, has endured controversies. In the past, those controversies were part of the spectacle.

Riders have been accused of cheating in dozens of ways: by hopping off their bikes and onto trains; by being towed by cars, with their bikes attached to the cars’ bumper by a wire.

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Fabian Cancellara won the Tour de France prologue. An X-ray of his bike did not find a tiny motor inside.Credit
United Photos/Reuters

Juicy tabloid stories existed even before there was a hunger for them.

Some riders have been accused of guzzling alcohol along the way — including carrying wine bottles on their bikes — to dull the physical pain of the race.

“I do think controversy is part of the rich history of the sport,” Stapleton said. “It’s not like you have a controlled message in cycling, something coming from a commissioner or a league office. Here, you have every team commenting on what’s going on and every big cycling fan commenting on what’s going on. For the past 100 years of the Tour de France, there has been controversy. The sport thrives off it and breeds it.”

But Cancellara has not been happy about it, at least when he is at the center of it. After his victory, he wondered if as many people watched him race on Saturday as watched the video of his alleged motorized doping on YouTube.

Others did not take the allegations so seriously. After the Garmin-Transitions rider David Zabriskie’s bike was X-rayed, the Garmin team director, Jonathan Vaughters, commented about it on Twitter.

“Zab’s bike is the first to go through the bike scanner,” Vaughters wrote. “They didn’t find a motor, but they did find an old 8 track of the Eagles.”

A version of this article appears in print on July 4, 2010, on page SP9 of the New York edition with the headline: No Tiny Motors, but Plenty of Mistrust As the Tour Gets Off to a Quick Start. Order Reprints|Today's Paper|Subscribe